FIG. 1 shows a conventional socket connection device 10 including a main body 11 and a slide rod 12 disposed in a slide passage 13 of the main body. One end of the slide rod 12 is formed with a shallow depression 14 and a deep depression 15. A steel ball 16 is inlaid in a through hole 17 of the main body. In normal state, the slide rod 12 is resiliently urged by a spring 18 and tends to move rightward according to FIG. 1. In this state, the shallow depression 14 is right under the through hole 17 and the steel ball 16 falls into the shallow depression 14 with its top edge outward protruding from the main body 11. When pushing a push rod 19, the slide rod 12 is moved leftward and the deep depression 15 is displaced to a position under the through hole 17. At this time, the steel ball falls into the deep depression 15 and retracts into the main body.
When fitting with a socket, the push rod 19 is first pressed to move the slide rod 12 and retract the steel ball 16 into the main body 11. Under such circumstance, the socket can be fitted with an insertion end 111 of the main body. Then, the push rod is released from the pressing force, whereby the spring 18 pushes the slide rod back to its home position where the steel ball again moves into the shallow depression 14. In this state, the steel ball protrudes from the main body to engage with a wall of a fitting hole of the socket. When taking off the socket, the push rod 19 is pushed to move the steel ball 16 into the main body and disengage the steel ball from the socket. At this time, the socket can be separated from the connection device 10.
According to the conventional socket connection device, no matter when connecting with the socket or disconnecting from the socket, a user needs to first press or pull the push rod to move the slide rod and retract the steel ball into the main body. This is quite inconvenient to the user.
It is impossible for the user to forcedly fit the socket with the main body without first retracting the steel ball into the main body. This is because that as shown in FIG. 2, the shallow depression 14 has an axial length L larger than the radius of the steel ball. That is, the center C, or to say the bottommost edge, of the steel ball falls onto a bottom wall 141 of the shallow depression 14. Therefore, when the socket touches the steel ball and exerts a pushing force onto the steel ball, the force exerted onto the steel ball is directly applied to the bottom wall 141 of the shallow depression 14. Therefore, it is impossible to make the slide rod 12 move. Accordingly, no matter how great the force exerted onto the steel ball by the socket is, the steel ball cannot be retracted into the main body.